Me bad. I did mix up HQ with IC. For the record, a regular techmarine is not an HQ in C:SM, BA, or GK codexes. He is an IC in C:SM and GK, but basic infantry in BA. MotF is only in C:SM, and is an SC IC and HQ slot vice Elites. So, at TM could join another infantry unit in an SR in C:SM and GK armies, but not in a BA army.